In Bridge, click on a filename, wait, then click again to rename (double-clicking is the shortcut to open the file)
Or you can righ-click on a thumbnail, and select rename.
But indeed, if you are running into an issue in bridge, you might want to post in the relevant forum, and please remember to give out details (your platform, the version you use, etc.)
(for this particular issue, is the file on a writable support, and not on a DVD/CD? that might explain why you cannot rename)